H. B. Moore1, P. Lawson1, M. Fragoso1, E. Gonzalez1, M. P. Chapman1, F. Gamboni1, S. Mitra1, C. A. Anderson1, A. Banerjee1, C. C. Silliman1, E. E. Moore1 1University Of Colorado,Surgery,Denver, COLORADO, USA
Introduction: The use of thrombelastography(TEG) in trauma has identified unique phenotypes of coagulopathy. Pathologic hyperfibrinolysis (excessive blood clot degradation) and fibrinolysis shutdown (impaired blood clot degradation) are associated with increased mortality compared to a low level of physiologic fibrinolysis. Investigating the regulation of fibrinolysis with animal models has been challenging and has low yield to clinical translation. We hypothesize that rats have a baseline fibrinolysis shutdown phenotype and require an exogenous challenge of a profibrinolytic to differentiate mechanisms that promote or inhibit fibrinolysis.
Methods: Fibrinolysis resistance was assessed by TEG with exogenous tissue plasminogen activator(tPA) titrations in rat whole blood. The experimental groups(n=9 per group) were: 1)tissue injury (laparotomy/bowel crush), 2) shock(hemorrhage to MAP < 25 mmHG), and 3) sham(arterial canulation and tracheostomy). Blood was sampled at 30 min, and assayed with native TEG challenged with taurcholic acid(TUCA, a known inhibitor of anti-fibrinolytic protein). The percent of remaining clot strength 30 min after reaching maximum amplitude(CL30) was used to measure clot resistance to fibrinolysis. Plasma was assayed for tPA concentration. Liver histology was assessed for organ damage due to oxygen sensitivity and receiving direct portal blood supply.
Results: Rat blood was resistant to exogenous tPA, CL30 at 150ng/ml(p=0.511) and 300ng/ml(p=0.931) was similar to baseline, while 600ng/ml(p=0.046) provoked fibrinolysis. Baseline(p=0.679) and post-procedure CL30(p=0.505) were not significantly different between groups when using a native TEG. TEG TUCA challenge showed no differences at baseline CL30(p=0.937); whereas, post-procedure there were differences in CL30 (Fig 1, p<0.001). This corresponded to similar plasma tPA concentrations(p=0.423) at baseline between rats and different tPA concentration(p=0.003) post procedure. The percent change in CL30 from baseline was increased in tissue injury compared to sham(p=0.048.); whereas, CL30 decreased in shock versus sham(p=0.048). Total tPA concentration was higher in the shock group compared to trauma(p=0.009) and sham(p=0.012). Histologic evidence of cellular damage was pronounced in trauma and shock compared to baseline.
Conclusion: The TEG TUCA challenge is capable of differentiating changes in clot stability with rats undergoing diverse stresses. Tissue injury inhibits fibrinolysis while shock promotes tPA mediated fibrinolysis, consistent with our recent clinical studies. This technical modification of TEG may be valuable for elucidating the mechanisms responsible for the spectrum of fibrinolysis observed following severe trauma.
